1. Field of the Invention
The present invention relates to the tapper with oil feeder which is mainly set to a tool driving spindle of NC machining center with automatic tool changer (ATC) so that it may be used.
A difinition of the NC machining center with ATC is an arrangement that cutting tools such as the tapper are housed in optional lines within a magazine being provided near to the machining center in advance, the magazine is rotated such that necessary cutting tool comes to its taking-out position in response to a unit selecting signal, the cutting tool is taken out by means of a manipulator, and a full automatic control based on instructions input by a computer covers an action of loading the tool driving spindle with the cutting tool or housing the cutting tool, etc. which completes its actuation, locating on the spindle, into the magazine.
In the case of performing the cutting process by such a automatic machine, in order to reduce a outbreak of frictional heat at the process, the cutting oil has to continue to be poured on the tool edge of the tap during maching as well as there is a necessity of giving rise to no impedance to the full automatic control.
2. Conventional technology
This kind of tapper with oil feeder may be classified, depending on its oil feeding system, into so-called side through type in which oil feeding is executed from the side face axially perpendicular to the tapper proper to the inside and a side through type in which the oil feeding is executing axially, i.e. from the shaft center to the inside. The former system is illustrated in FIG. 5, whereas the latter is illustrated in FIG. 6.
Referring first to FIG. 5, a description of the structure of the conventional tapper with oil feeder is made; 1 is a tapper proper, on the base end side of which a shank part 3 to be fitted into the tool driving spindle 2 is located. A mounting hole 4 of comparatively larger diameter is axially made in the tapper proper, the shaft to be driven 5 is mounted in said mounting hole 4 in such a way that said shaft to be driven 5 can be freely removed in an axial direction, and, similarly to such an embodiment of the present invention as shown in FIG. 2, guide grooves 6 and 7 (not shown in FIG. 5) which are made on the internal periphery of the tapper proper 1 and the external periphery of the shaft to be driven 5 corresponding to said internal periphery thereof, respectively, a guide ball 8 being fitted into the part between these guide grooves 6 and 7, the resultant guide mechanism of which causes the shaft to be driven 5 to be rotated as one unit with the tapper proper 1 without being obstructed its rotational motion by the foregoing axial removal. The shaft to be driven 5, formed to be of cylindrical shape the entire inside part of which is integrally extended from the shaft center of the tapper proper 1 toward the top end thereof settled near the hollow section 30 of the base end side of said shaft 5, rings for receiving springs 10 are supported for being slidably fitted at the external peripheral side of the top end part of the tension shaft 9, compression springs 11 which pressurize the shaft to be driven 5 up to the top end side thereof are provided between the rings for receiving springs 10 and the tapper proper 1 (the base end face of the mounting hole 4), tension springs 13 which pressurize the shaft to be driven 5 up to the base end side with a pressurizing force slightly weaker than that of the foregoing pressurizing action up to the top, are provided between the rings for receiving springs 10 and pieces for receiving springs 12 being located on the shaft to be driven 5, and engerized resilient force, taking place in each of directions opposite to each other, by both the springs 11 and 13 against the shaft to be driven (floating shaft) 5 causes said shaft to be driven 5 to be supported under the floating state in the tapper proper 1. By means of a connecting and removing device 14, provided on the top end side of the shaft to be driven 15, a tap holder 16 for holding the tap 15 is detachably mounted to the shaft to be driven 5.
A statement of the oil feeder may show that an annular supporting casing 17 is rotatably supported on the external peripheral side of the tapper proper 1 by bearings 18, a cylinder for receiving oil 19, being axially extended, is integrally formed on the external peripheral side of said supporting casing 17, and a hollow pin 20, cylindrical, is slidably fitted into said cylinder 19, while being resiliently pressed toward the base end side by springs 21. A detent member 22, which is radially projected toward the tapper proper 1, is provided on the external peripheral side of the hollow pin 20, in a manner corresponding to said detent member 22, a recessed section to be notched 23 with which the detent member 22 is engaged is formed on the tapper proper 1, and a check vavle comprising springs 24 and a ball valve which undergoes a resilient force from said springs 24 is provided in the inside of the hollow pin 20. The oil feeding passage 27 capable of communicating with the hollow pin 20 is formed on a oil feeding block 26 which is fixed to a fixing member 25 which supports the spindle 2. A communicating passage is radially formed in the cylinder for receiving oil 19, a passage through which the oil flows 29, which communicates with said communicating passage 28, is formed in the tapper proper 1, connecting passages 31, which makes a connection between the hollow section 30 and the above mentioned passage through which the oil flows 29 is formed in the shaft to be driven 5, and said hollow section 30 communicates by way of the passage 32 being provided on the top end part of the tension shaft 9 with the tap holder 16 mounted on the top end part of the shaft to be driven 5 and the oil passages 33 and 34 provided on the tap 15 being held by said tap holder 16.
In order to use such a oil feeder, by means of fitting the detent member 22, which is illustrated by a chain line in FIG. 5, into the recessed section to be notched 23 which is located on the side of the tapper proper 1, the supporting casing 17 is adapted to be held on the orientation of the tapper proper 1, under such a oil feeder's state of which the tapper is housed in the predetermined magazine. At the work, by means of engaging the shank part 3 with the spindle 2, while grasping the section to be grasped 35 with the manipulator, at the same time when the hollow pin 20 communicates with a oil feeding passage 27 of a oil feeding block 26, a resultant pressurizing of said hollow pin 20 by said oil feeding passage 27 will cause said hollow pin 20 to makes a retreat against the resilient force from the spring 21, upon an occurence of which the detent member 22 in turn will come off out of the recessed section to be notched 23, whereby a relative rotation of the shaft to be driven 5 with regard to the supporting casing 17 is ready to be commenced.
Of course, a rotation of the tapper proper 1 is accompanied with that of the shaft to be driven 5, the tap located on its top end side causing a tapped hole to be made, an impact taking place when the tap 15 gets in touch with the workpiece to be machined is reduced by damping springs 11 and, at the same time, during the intermediate course of making the tapped hole, the shaft to be driven 5 makes an advance independently of the tapper proper 1, while being guided also by the tapped hole by itself, upon completion of making the tapped hole, a reversive rotation of the shaft to be driven 5 leading to a commencement of the retreat of said shaft to be driven 5 under the assistance from a guidance by the tapped hole by itself as well as a tensile force by the tension springs 13. For this reason, in addition to a reduction of the removal stroke distance of the tapper proper 1 by itself, the shaft to be driven 5 can move forward and/or backward, while being axially balanced its motion in an axial direction by means of both the springs 11 and 13.
The cutting oil which is fed from the oil feeding block 26 through the hollow pin 20 and the cylinder for receiving oil 19, is received from the communicating passage 28 into the passage through which the oil flows, from which said cutting oil passes the connecting passages 31, being fed into the hollow section 30 of the shaft to be driven 5, and it is supplied through the passage 32 to the oil passage 34 of the tap 15 so that it is finally adapted to be poured on the tapped hole where cutting is under way.
According to the conventional tapper with oil feeder, the structure and actuating conditions of which are referred to as above, there may be the following shortcomings:
Namely, during the intermediate course of cutting process, as shown by an arrow A of FIG. 5, the cutting oil passes from the passage through which the oil flows 29 through the hollow section 30 of the shaft to be driven 5, and is supplied from the passage 32 to the side of the tap 15, whereas, as shown by an arrow B, it, passing the hollow section 30, is fed into the side of the base end part of the shaft to be driven 5, whereby it comes to pressurize the end face 5a thereof. In that case, although any serious problem does not occur, if the pressure of the cutting oil is relatively lower, in the cases where such an pressure is increased, the oil passage 34 of the tap 15 is clogged, or a resistance in the tube is larger, because the oil passage 34 is small in diameter, the hydraulic pressure being applied to the end face 5a of the shaft to be driven 5 results in being increased, due to which the shaft to be driven 5, being pushed by such a pressure, gets out of the foregoing fine balanced state, making a rapid advance proportionally to a rise in pressure so that the situation occurs in which the tap 15 is damaged or there is an inability in fabricating accurately the hole to be tapped.
Such a spindle through type tapper as shown in FIG. 6 also possesses the forgoing shortcomings.
If a description putting a focuse only on different points from the side through type tapper of FIG. 5 is made, the spindle through type tapper employs the construction in which a passage for receiving oil 36, which communicates with the oil feeding passage (not shown) being provided on the shaft center of the spindle 2, is axially provided in the shank part 3 of the tapper proper 1, and, at the same time, a oil flowing pipe 37, which, passage the hollow section 30 of the shaft to be driven 5, is extended to the top end side, is extendedly provided in the tapper proper 1, communicating with the passage for receiving oil 36. The ring for receiving spring 10 is fitted in the external peripheral side of the above-mentioned oil flowing pipe 37, supporting both the springs 11 and 12. For this reason, some portions of the cutting oil, which, passing from the oil feeding passage 36 to the oil flowing pipe 37, is supplied to the side of the tap 15, is fed from the hollow section of the shaft to be driven 5 to the base end side so that they pressurize the end face 5a of the shaft to be driven 5, being forced to be fed to the top end side due to the pressure differential-area corresponding to the internal diameter of the oil flowing pipe 37, thereby producing the foregoing trobules.